1. Field of the Invention
The present invention relates to an outboard motor.
2. Description of the Related Art
Outboard motors provided with a catalyst to clean the exhaust from the engine are known. For example, in the outboard motor disclosed in U.S. Pat. No. 5,554,057, a catalyst is disposed below the engine. It is disclosed that water is kept out of the catalyst by disposing a heat accumulator downstream of the catalyst.
In U.S. Pat. No. 7,698,889, which relates to a stern drive rather than an outboard motor, it is disclosed that water is kept out of the catalyst by disposing a non-catalytic porous member downstream of the catalyst.
In the outboard motor disclosed in U.S. Patent Application Publication 2009/0215341, an exhaust pipe extends upward from a cylinder, passes above the cylinder, and extends downward at the opposite side of the cylinder. A moisture capture member is disposed in a portion of the exhaust pipe. The portion is positioned above the cylinder.
A water capture member and catalyst member are disposed in the same exhaust passage, whereby water exposure of an oxygen sensor disposed downstream from a catalyst member can be minimized. Such a structure is manufactured by, e.g., press-fitting two honeycomb structures into the same exhaust passage. In this case, the honeycomb structure on the inner side is inserted into the exhaust passage, after which the honeycomb structure on the outer side is inserted into the exhaust passage. Therefore, it is possible that the surface roughness on the inner surface of the exhaust passage will be reduced by friction between the exhaust passage and the previously press-fitted honeycomb structure. In this case, the holding function of the exhaust passage in relation to the honeycomb structure on the outer side is reduced.